This invention relates in general to layered imaging members, inclusive of flexible members and substantially rigid members, or OPC members comprised, for example, of a photogenerating layer and a charge transport layer. The charge transport layer comprises in embodiments a charge transport compound, a resin binder, and a vinyl containing organic compound which is substantially compatible with the binder resin and functions primarily as an antiozonant, and which antiozonant prevents, or minimizes resin binder molecular degradation by exposure to ozone. The vinyl containing compound can be a solid or a high boiling liquid having a boiling point of at least about 200° C. to, for example, prevent its loss from the charge transport layer due to evaporation. The charge transport layer in embodiments may also comprise a hindered phenol antioxidant.
More specifically, the present invention relates to an electrophotographic imaging member comprised in sequence of a supporting substrate, a hole blocking layer, an adhesive layer, a photogenerating layer, and a charge transport layer containing charge, especially hole transport components, a polymer binder, a vinyl containing organic compound which is preferably compatible with the polymer binder and functions as an effective antiozonant to eliminate or suppress the polymer binder molecular chain scission to permit the prevention of chain backbone break down into low molecular weight polymer fragments that converts the charge transport layer into a brittle coating layer. Compatibility of the vinyl containing organic compound is of value to enable formation of a homogeneous charge transport material blend with the binder polymer so that presence of the vinyl organic compound avoids or minimizes the development of phase separation in the resulting charge transport layer material matrix. Furthermore, in embodiments the invention electrophotographic imaging members may also contain a plurality of layers, such as two charge transport layers comprising a first (bottom) charge transport layer which is in contiguous contact with the photogenerating layer, and a second (top) charge transport layer coated over the first charge transport layer. The bottom charge transport layer can comprise a binary solid solution of a charge transport compound and a polymer binder, whereas the top charge transport layer is comprised of a charge transport compound, a polymer binder, an effective antiozonant vinyl containing organic compound, and also in embodiments an oxidative stabilizer hindered phenol to prevent charge lateral conductive migration (LCM) associated print defects observable in the output printed copy. Coating of the dual transport layers in separate passes provides, for example, the benefit of minimizing the transport layers thickness variations since these thickness variations can cause undesirable image defects printout (referred to as rain drops) and thus degrade the copy quality.
In specific embodiments of the present invention there are provided imaging members containing an exposed charge transport layer which comprises an organic compound additive with a vinyl terminated group or groups, and which functions primarily as an antiozonant, and which organic compound is, for example, an unsaturated carbonate compound of the following Formula AR1—O—CO2—R2—O—R2—CO2—O—R1,wherein R1 is unsaturated vinyl chain with, for example, from about 3 to about 40 carbon atoms, and wherein R2 is different from R1, and wherein R2 is selected from the group consisting of a) a nonsubstituted aliphatic chain with, for example, from about 1 to about 50 carbon atoms, b) a substituted aliphatic chain with, for example, from about 1 to about 50 carbon atoms, c) an unsubstituted aromatic group with, for example, from about 6 to about 30 carbon atoms, d) a substituted aromatic group with, for example, from about 6 to about 30 carbon atoms, e) an unsubstituted heterocyclic group with, for example, from about 3 to about 40 carbons, and f) a substituted heterocyclic group with, for example, from about 3 to about 40 carbons wherein the substituents are selected, for example, from the group consisting of aliphatic groups with from about 1 to about 50 carbons, cycloaliphatic groups with from about 3 to about 28 carbons, halides, aromatic groups with from about 6 to about 30 carbons, nitro groups, amino groups, amido groups, cyano groups, and sulfonyl groups. Moreover, in embodiments the Formula A additive illustrated herein with R1 and R2 being the vinyl termination group and alkylene, such as ethylene segments, respectively; one specific monomer carbonate liquid of Formula A is, for example, a diethylene glycol bis(allyl carbonate) as represented byCH2═CH—CH2—O—CO—O—CH2—CH2—O—CH2—CH2—O—CO—O—CH2—CH═CH2.
Alternatively, in embodiments of the present invention the imaging members are comprised of an unsaturated carbonate compound of bisphenol A carbonate of the following Formula B wherein R1 is an unsaturated vinyl chain having from about 3 to about 40 carbon atoms, and R3 and R4 are the same or different, and are selected from the group consisting of a) an unsubstituted aliphatic group having from about 1 to about 50 carbon atoms, and b) a substituted aliphatic group having from about 1 to about 50 carbon atoms, wherein the substituents are selected from the group consisting of aliphatic groups having from about 1 to about 50 carbons, cycloaliphatic groups having from about 3 to about 28 carbon atoms, halides, aromatic groups having from about 6 to about 30 carbons, nitro groups, amino groups, amido groups, sulfonyl groups, and cyano groups. In a specific embodiment, the R1 in bisphenol A carbonate monomer of Formula B is an allyl group.
In addition, the imaging members in embodiments of the present invention may contain an exposed charge transport layer which may further comprise a low molecular weight polystyrene having a vinyl end group as illustrated in Formula C wherein x or R illustrated herein represents the degrees of polymerization and is an integer of, for example, from 0 to 20, and more specifically, from about 7 to about 15.
The imaging members of the present invention avoid or minimize attacks by ozone species present in the corona generated effluents to thereby minimize charge transport layer cracking, wear, and defects and deletions in the printed copy; and more specially, wherein there is minimized in the charge transport layer binder, such as a polycarbonate binder, the chain scission caused primarily by ozonolysis, which in turn results in undesirable cracking in the charge transport layer of the imaging member. The protection against ozone attack and polymer binder chain scission, as a result of the incorporation of a vinyl containing organic compound in the charge transport layer, can be illustrated with reference the following chemical reaction 
The exposed charge transport layer may also include an antioxidant, such as a hindered phenol, thus deletion (LCM) defects copy printouts caused primarily by the imaging members oxidative interaction between the charge transport compound and the corona species of, for example, nitrogen oxides NOx, and can be eliminated or suppressed.
Advantages associated with the imaging members of the present invention, in embodiments thereof include, for example, the avoidance or minimization of cracking in the charge transport layer, especially microcracking manifestation appearing in the form of defect bands in a copy printout. The microcracks are generated by the interaction of corona effluents and corona emissions typically found to be, for example, from about 5 to about 10 microns in width, and from about 500 to about 800 microns in length resulting in print defects and adversely affecting the functionality while prematurely shortening the service of the member. Moreover, polymer binder chain degradation as a result of ozonolysis attack can also produce another adverse outcome because such degradation is breaking down the molecular chain length of the binder rendering the transport more susceptible to wear against cleaning blades and other contacting subsystems mechanical interactions under a normal imaging member machine functioning condition.
The imaging members may also contain in the exposed charge transport layer a light shock resisting or reducing agent, such as 3,3′,5,5′-tetra-tert-butyl-4,4′-diphenoquinone (DPQ); 5,6,11,12-tetraphenyl naphthacene (Rubrene); 2,2′-[cyclohexylidenebis[(2-methyl-4,1-phenylene)azo]]bis[4-cyclohexyl-(9Cl)]; perinones; perylenes; and dibromo anthanthrone (DBA) for minimizing or eliminating light shock effect to thereby impart the imaging member with added excellent electrical functions, improved mechanical characteristics, and copy print out quality enhancements.
Processes of imaging, especially xerographic imaging and printing, including digital, are also encompassed by the present invention. More specifically, the layered photoconductive imaging members of the present invention can be selected for a number of different known imaging and printing processes including, for example, electrophotographic imaging processes, especially xerographic imaging and printing processes wherein charged latent images are rendered visible with toner compositions of an appropriate charge polarity. Moreover, the imaging members of this invention are useful in color xerographic applications, particularly high-speed color copying and printing processes, and which members are, in embodiments, sensitive in the wavelength region of, for example, from about 400 to about 900 nanometers, and in particular from about 550 to about 850 nanometers, thus diode lasers can be selected as the light source.